apeforest commented on a change in pull request #15120: [bug] fix higher grad
log
URL: https://github.com/apache/incubator-mxnet/pull/15120#discussion_r295504687
##########
File path: src/operator/tensor/elemwise_unary_op_basic.cc
##########
@@ -1090,68 +1090,84 @@
MXNET_OPERATOR_REGISTER_BINARY_WITH_SPARSE_CPU_DR(_backward_log,
unary_bwd<mshadow_op::log_grad>)
.set_attr<nnvm::FGradient>("FGradient",
[](const nnvm::NodePtr& n, const std::vector<nnvm::NodeEntry>& ograds) {
- // For f(x) -> f = log
+ // ograds[0]: dL/dxgrad
+ // inputs[0]: dL/dy
+ // inputs[1]: x
+ // f(x) = y = log(x)
+ // f'(x) = 1/x
// f''(x) = -1 * (f'(x) * f'(x))
- auto gx = nnvm::NodeEntry{n};
- auto ggx_mid = MakeNode("elemwise_mul", n->attrs.name +
"_backward_mid_grad_grad",
- {gx, gx}, nullptr, &n);
- auto ggx = MakeNode("negative", n->attrs.name + "_backward_grad_grad",
- {nnvm::NodeEntry{ggx_mid}}, nullptr, &n);
+ auto dydx_mul_dldy = nnvm::NodeEntry{n}; // f'(x) * head_grads
+ auto dlogx = MakeNode("reciprocal", n->attrs.name + "_dlogx",
+ {n->inputs[1]}, nullptr, &n);
+ auto d2ydx2_mid = MakeNode("elemwise_mul", n->attrs.name + "_d2ydx2_mid",
+ {dydx_mul_dldy, nnvm::NodeEntry{dlogx}}, nullptr,
&n);
+ auto d2ydx2 = MakeNode("negative", n->attrs.name + "_d2ydx2",
+ {nnvm::NodeEntry{d2ydx2_mid}}, nullptr, &n);
std::vector<nnvm::NodeEntry> ret;
ret.emplace_back(MakeNode("elemwise_mul", n->attrs.name +
"_backward_grad_grad",
- {ograds[0], gx}, nullptr, &n));
+ {ograds[0], nnvm::NodeEntry{dlogx}}, nullptr,
&n));
ret.emplace_back(MakeNode("elemwise_mul", n->attrs.name +
"_backward_grad_grad_inp",
- {ograds[0], nnvm::NodeEntry{ggx}}, nullptr, &n));
+ {ograds[0], nnvm::NodeEntry{d2ydx2}}, nullptr,
&n));
return ret;
});
MXNET_OPERATOR_REGISTER_BINARY_WITH_SPARSE_CPU_DR(_backward_log10,
unary_bwd<mshadow_op::log10_grad>)
.set_attr<nnvm::FGradient>("FGradient",
[](const nnvm::NodePtr& n, const std::vector<nnvm::NodeEntry>& ograds) {
- // For f(x) -> f = log10
+ // ograds[0]: dL/dxgrad
+ // inputs[0]: dL/dy
+ // inputs[1]: x
+ // f(x) = y = log10(x)
// f'(x) = 1 / (log(10) * x)
// f''(x) = -1 * (f'(x) * 1/x)
- auto gx = nnvm::NodeEntry{n, 0, 0};
- auto g_lx = MakeNode("reciprocal", n->attrs.name + "_backward_log_grad",
+ auto dydx_mul_dldy = nnvm::NodeEntry{n}; // f'(x) * head_grads
+ auto dydx = MakeNode("elemwise_div", n->attrs.name + "_dydx",
+ {n->inputs[0]}, nullptr, &n);
+ auto dlogx = MakeNode("reciprocal", n->attrs.name + "_dlogx",
{n->inputs[1]}, nullptr, &n);
- auto ggx_mid = MakeNode("elemwise_mul", n->attrs.name +
"_backward_mid_grad_grad",
- {gx, nnvm::NodeEntry{g_lx}}, nullptr, &n);
- auto ggx = MakeNode("negative", n->attrs.name + "_backward_grad_grad",
- {nnvm::NodeEntry{ggx_mid}}, nullptr, &n);
+ auto d2ydx2_mid = MakeNode("elemwise_mul", n->attrs.name + "_d2ydx2_mid",
+ {dydx_mul_dldy, nnvm::NodeEntry{dlogx}}, nullptr,
&n);
+ auto d2ydx2 = MakeNode("negative", n->attrs.name + "_d2ydx2",
+ {nnvm::NodeEntry{d2ydx2_mid}}, nullptr, &n);
std::vector<nnvm::NodeEntry> ret;
ret.emplace_back(MakeNode("elemwise_mul", n->attrs.name +
"_backward_grad_grad",
- {ograds[0], gx}, nullptr, &n));
+ {ograds[0], nnvm::NodeEntry{dydx}}, nullptr, &n));
ret.emplace_back(MakeNode("elemwise_mul", n->attrs.name +
"_backward_grad_grad_inp",
- {ograds[0], nnvm::NodeEntry{ggx}}, nullptr, &n));
+ {ograds[0], nnvm::NodeEntry{d2ydx2}}, nullptr,
&n));
return ret;
});
MXNET_OPERATOR_REGISTER_BINARY_WITH_SPARSE_CPU_DR(_backward_log2,
unary_bwd<mshadow_op::log2_grad>)
.set_attr<nnvm::FGradient>("FGradient",
[](const nnvm::NodePtr& n, const std::vector<nnvm::NodeEntry>& ograds) {
- // For f(x) -> f = log2
+ // ograds[0]: dL/dxgrad
+ // inputs[0]: dL/dy
+ // inputs[1]: x
+ // f(x) = y = log10(x)
Review comment:
```suggestion
// f(x) = y = log2(x)
```
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